The principal investigator requests support to continue studies of the retinal and choroidal circulation of monkeys by the technique of relative retinal blood flow estimation using densitometry readings from serial fluorescein angiograms. The specific problems to receive first attention will be (1) studies of temporary occlusion of the central retinal artery, and assessment of subsequent vascular and metabolic changes in the inner layers of retina; (2) studies of the pharmacologic effect on retinal blood flow of vaso-active amines; and (3) studies of the regulation of choroidal supply to the optic disc. Concurrently we will equip a separate laboratory to perform ocular blood flow studies by the method of Krypton-85 wash out curves (Friedman et al) to provide a complementary and corroborative method for our photographic studies.